The present invention relates to a material having a high absorptive capacity for use in an absorbent structure in an absorbent product, such as a sanitary towel, tampon, nappy and the like, and also to an absorbent product which includes such an absorbent structure.
Absorbent products of this nature are known in a number of embodiments. Conventionally, the absorptive body in these products is produced by cellulose pulp, in rolls, bales or sheets, for example, being dry-defibred and converted, in fluff form, into a pulp mat, sometimes together with admixture of so-called superabsorbents, which are highly absorbent materials having the ability to absorb several times their own weight of water or body liquid.
The absorptive body can also contain further constituents, for example in order to improve its liquid-assimilating properties or its liquid-dispersing properties, or to increase its cohesiveness and ability to resist deformation during use.
In the case of most hygiene products, it is desirable for the product to be thin so that it can be worn as discretely as possible. In order to achieve this, the pulp body is often compressed, partly in order to reduce its bulk and partly in order to increase its liquid-dispersing ability.
A major problem with these products is that of combining the need to make a thin product with the need to have a high overall absorptive capacity. A substantially greater absorptive capacity can be achieved by adding highly-absorbent material to the absorptive body. A method of adding highly absorbent material to an absorbent structure is described in European Patent 122 042, in which a mixture of hydrophilic fibres and superabsorbent particles is air-laid to form a web and compressed to a density of from 0.15 to approximately 1.0 g/cm.sup.3. The superabsorbent material is normally available in the form of granules or small particles which can be difficult to bind satisfactorily to the absorbent structure. Superabsorbent materials are also expensive, for which reason other solutions have been sought. Furthermore, the majority of superabsorbents are produced from synthetic, non-biodegradable polymers, for example polyacrylates. There is a need, therefore, for materials which have a high absorptive capacity and which at the same time are biodegradable.
Another problem with hygiene articles is that of so-called rewetting, i.e. when body liquid which has already been absorbed is pressed back towards the skin of the user by external influence, for example when the user sits down. It is, thus, a general requirement that the side of the product facing the user should be as dry as possible. By means of selecting absorbent materials which bind the absorbed liquid to a high degree, this problem can be reduced.
Another problem with absorbent structures in hygiene articles is that, at the high densities which are advantageous for liquid dispersal, it tends to be difficult to make such structures sufficiently soft and flexible to meet the high present-day demands for comfort in relation to this type of article.
Another problem with absorbent structures in hygiene articles is that of achieving high speeds of absorption and rapid assimilation of liquid, especially when repeated wetting occurs. When conventional super-absorbents are used, gel blocking can easily occur in the material, and the speed of absorption decreases with repeated wetting. There has therefore been a demand for highly absorbent materials which do not have any gel blocking tendency.
It is known from European Patent EP 444 073 to use dry forming in order to manufacture web-shaped pulp for subsequent defibering, so-called dry-formed reel pulp. The strength of the pressed web of flash-dried fibres, having a grammage of 300-1500 g/m.sup.2 and a density of 550-1000 kg/m.sup.3, is such that the web can be rolled up or handled in sheet form for storage and transport. It is easy to defibre and is normally meant to be converted into fluff form in order to be used for producing absorptive bodies in nappies, sanitary towels and similar products.